In the data processing installations where the information is processed en masse in parallel, it is more and more necessary to have available transmission lines called "buses", of high performance, capable of transmitting several Gbits/s.
Only optical technology today is capable of providing throughputs greater than a Gbits/s, simultaneously over a large number of links, with interfaces of small dimensions and low consumption.
The European Patent Document 0 196 933 describes a system making it possible to establish optical links between circuits of the same apparatus. It necessitates a transparent sheet forming the rear panel of the housing, light sources and receivers carried by the printed circuits and situated, preferably, in immediate proximity to the said rear panel. The diffracting optical elements and reflector elements are judiciously placed on the rear panel in order to transmit the light between one or more emitters and one or more receivers by creating multiple reflections in the transparent sheet. This principle implies a certain optical route "in air" outside any light guide of the fibre optic type.
Moreover, it is relatively constricting as far as the installation of the components on the printed circuits and the positioning of the latter are concerned.